What is this collegue's login name?

What is this collegue's login name?

My collegues often forget to mention their logon account name when calling the helpdesk, and the helpdesk doesn't always ask either. I suppose they expect me to know all 1500+ accounts by heart.
With (native) Windows Server 2003 commands only:

    DSQUERY USER -name *lastname* | DSGET USER -samid -display

Note:

Windows Server 2003's "DSTools" will work fine in Windows 2000 and XP too, when copied. Keep in mind, however, that some Windows Server 2003 Active Directory functionality is not available in Windows 2000 Active Directories.